Objectives The aim of this study was to investigate associations between psychosocial working conditions, occupational groups defined by sector, and disability pension (DP) with mental diagnoses while accounting for familial confounding.

Methods A prospective population-based cohort study was conducted, including all Swedish twins who, in January 1993, were living and working in Sweden and not on old-age pension or DP (N=42 715). The twins were followed from 1993-2008 regarding DP. Data on DP, exposures, and covariates were obtained from national registries. Cox proportional hazards regression models with hazard ratios (HR) and 95% confidence intervals (95% CI) were constructed for the whole cohort, and for discordant twin pairs.

Results The associations for the whole cohort between DP with mental diagnoses and (i) job demands (HR 1.23, 95% CI 1.06-1.43), (ii) job control (HR 0.91, 95% CI 0.83-0.99), (iii) healthcare and social work (HR 1.41, 95% CI 1.04-1.92), and (iv) service and military work (HR 2.07, 95% CI 1.37-3.14) remained after accounting for possible confounders, including familial factors, while the associations between DP and (i) social support, (ii) type of jobs, and (iii) some of the occupational groups were attenuated, becoming non-significant. In the discordant twin pair analyses, commercial work was significantly associated with lower risk of DP (HR 0.55, 95% CI 0.32-0.95).

Conclusions One unit increase in job demands and working in the occupational groups healthcare and social work or service and military work seem to be risk factors of DP with mental diagnoses, independent from various background factors including familial ones. However, one unit increase in job control or working in commercial work seem to be protective factors of such DP, accounting for confounding factors of this study.

In general, work is considered to be positive for mental health (1, 2). However, work can also be a potential risk factor for mental ill-health in that it might contribute to the development of and/or prolong a mental disorder (3). A mental disorder may lead to sickness absence and even to permanent work incapacity giving rise to the granting of a disability pension (DP) (3). In recent decades, the incidences of both mental disorders (4) and DP due to mental diagnoses (5) have increased. At present, mental diagnoses constitute the most common reason for DP (5, 6). Still, there is a lack of studies of work-related risk factors for being granted DP due to mental diagnoses (7).

Psychosocial working conditions can be risk factors of this kind and have often been measured using the Job Demand-Control-Support model (8-10). According to this model, jobs with high demands, low control, and/ or low social support, and jobs with a combination of high demands and low control (high strain) and low social support (iso strain) are associated with increased risks of sickness absence/DP due to mental diagnoses (7, 11-18). In most of the previous studies of psychosocial working conditions, self-report surveys have been used to assess these factors (11, 15-19), but fewer studies have measured these working conditions by applying a validated job exposure matrix (JEM) (20-22), based on mean scores of job demands and control and social support in different occupations. Moreover, only a few previous studies are based on population-based cohorts (23), which limits the generalizability of their findings.

Although the right to be granted DP is related to the individual's work history, there are only a small number of studies (24-29) that have investigated the association between occupation and risk of DP. …